| 1. |
- Hawkes, Jeffrey A., et al.
(författare)
-
An international laboratory comparison of dissolved organic matter composition by high resolution mass spectrometry : Are we getting the same answer?
- 2020
-
Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 18:6, s. 235-258
-
Tidskriftsartikel (refereegranskat)abstract
- High-resolution mass spectrometry (HRMS) has become a vital tool for dissolved organic matter (DOM) characterization. The upward trend in HRMS analysis of DOM presents challenges in data comparison and interpretation among laboratories operating instruments with differing performance and user operating conditions. It is therefore essential that the community establishes metric ranges and compositional trends for data comparison with reference samples so that data can be robustly compared among research groups. To this end, four identically prepared DOM samples were each measured by 16 laboratories, using 17 commercially purchased instruments, using positive-ion and negative-ion mode electrospray ionization (ESI) HRMS analyses. The instruments identified similar to 1000 common ions in both negative- and positive-ion modes over a wide range of m/z values and chemical space, as determined by van Krevelen diagrams. Calculated metrics of abundance-weighted average indices (H/C, O/C, aromaticity and m/z) of the commonly detected ions showed that hydrogen saturation and aromaticity were consistent for each reference sample across the instruments, while average mass and oxygenation were more affected by differences in instrument type and settings. In this paper we present 32 metric values for future benchmarking. The metric values were obtained for the four different parameters from four samples in two ionization modes and can be used in future work to evaluate the performance of HRMS instruments.
|
|
| 2. |
|
|
| 3. |
- Hawkes, Jeffrey A., et al.
(författare)
-
Regional diversity of complex dissolved organic matter across forested hemiboreal headwater streams
- 2018
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic matter (DOM) from soils enters the aquatic environment via headwater streams. Thereafter, it is gradually transformed, removed by sedimentation, and mineralised. Due to the proximity to the terrestrial source and short water residence time, the extent of transformation is minimal in headwaters. DOM has variable composition across inland waters, but the amount of variability in the terrestrial end member is unknown. This gap in knowledge is crucial considering the potential impact large variability would have on modelling DOM degradation. Here, we used a novel liquid chromatography –mass spectrometry method to characterise DOM in 74 randomly selected, forested headwater streams in an 87,000 km2 region of southeast Sweden. We found a large degree of sample similarity across this region, with Bray-Curtis dissimilarity values averaging 8.4 ± 3.0% (mean ± SD). The identified variability could be reduced to two principle coordinates, correlating to varying groundwater flow-paths and regional mean temperature. Our results indicate that despite reproducible effects of groundwater geochemistry and climate, the composition of DOM is remarkably similar across catchments already as it leaves the terrestrial environment, rather than becoming homogeneous as different headwaters and sub-catchments mix.
|
|
| 4. |
|
|
| 5. |
- Radoman, Nikola, 1985-
(författare)
-
Enrichment of biogenic and anthropogenic organic substances on sea spray aerosols
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The world’s oceans are the source of one of the most abundant types of natural aerosols, namely sea spray aerosols (SSA). By scattering solar radiation, SSA play a significant role in controlling the Earth’s radiation budget, while they are also involved in the formation of clouds, acting as cloud condensation nuclei (CCN). To understand the connection between biogeochemical processes occurring in the ocean and in the atmosphere, it is crucial to gain better insight into the detailed chemical composition of SSA, which broadly consists of sea salt and marine organic matter. The aim of this thesis is to (1) better understand the impact of ocean biological activity on the chemical composition of SSA and (2) improve the knowledge on the ability of SSA to transport different organic pollutants to the atmosphere. In Paper I it was shown that changes in the composition of marine organic matter during a phytoplankton bloom in the North Atlantic were clearly reflected in the composition of generated SSA. Increased chlorophyll a concentration in seawater was correlated with the presence of lipid-like compounds with high H/C and low O/C atomic ratios, and a consistent trend in chemical composition was observed for subsurface water, the surface microlayer, and generated SSA. Although the effect of biological processes on the composition of SSA organic matter was clear, in Paper II it was shown that during the phytoplankton bloom, the abundance of organic matter in SSA was fairly constant, without any significant influence on their CCN activity or the particle production flux. Paper III provided a mechanistic understanding of the enrichment of different cationic surfactants (CSs) in SSA through experiments conducted using a sea spray simulation chamber. It was shown that enrichment of the CSs was primarily driven by the alkyl chain length of the CSs but also affected by the different functional groups in the CSs. The highest enrichment of CSs on SSA was observed for quaternary amines followed by primary and tertiary amines. Interaction with dissolved humic acid was shown to decrease the enrichment of longer-chain amines while the enrichment was increased for shorter-chain ones. When the plunging jet flow rate was increased, enrichment in SSA was shown to increase, especially for lower water concentrations of surface-active compounds. The purpose of Paper IV was to improve the understanding of the enrichment behavior of perfluoroalkyl acids (PFAAs), which are strong anionic surfactants. Similar to CSs, it was shown that increasing the plunging jet flow increased the enrichment on SSA, from 43-88% for different PFAAs. The effect of different inorganic salts present in seawater on enrichment was also tested. Compared to chamber experiments prepared with ~35% NaCl water matrix, it was shown that the presence of other seawater ions, namely Ca2+ and Mg2+, increased the enrichment of some PFAAs, especially for those with longer perfluoroalkyl chains.
|
|
| 6. |
|
|
| 7. |
- Radoman, Nikola, et al.
(författare)
-
Probing the impact of a phytoplankton bloom on the chemistry of nascent sea spray aerosol using high-resolution mass spectrometry
- 2022
-
Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2634-3606. ; 2:5, s. 1152-1169
-
Tidskriftsartikel (refereegranskat)abstract
- Sea spray aerosol is the largest natural source of aerosol to Earth's atmosphere with significant impacts on climate. Despite this, estimates of the impact of sea spray aerosol on Earth's radiation budget are highly uncertain due to an overall lack of understanding of the physical and chemical factors controlling its composition. Critically, results from studies probing the importance of oceanic biological activity on the amount and type of organic matter present in nascent sea spray aerosol have been ambiguous. Some field studies have shown a relationship between the organic fraction of sea spray aerosol and oceanic primary productivity while others have reported no such relationships. Given this, we have probed the composition of seawater and nascent sea spray aerosol during a phytoplankton bloom in the North Atlantic using a novel liquid chromatography-mass spectrometry method. We observed that the composition of dissolved organic matter present in seawater changed as the phytoplankton bloom progressed over an 18 day period. Further, we observed changes to both the chemical composition of the organic matter present in seawater and the chemical composition of the organic matter present in the sea spray aerosol despite the organic matter mass fraction of the aerosol remaining unchanged. More specifically, we observed that the nascent sea spray aerosol became progressively more enriched in surface-active organic substances as the bloom progressed and that the sea spray aerosol had a distinct organic matter composition compared to the seawater. Thus, our work provides additional insight into the biological dependence of nascent sea spray aerosol composition.
|
|
